The use of power lines for the communication of data is well known. Power line communication (PLC) systems and methods have been used in a variety of applications, including the control of household appliances. One manufacturer, X10 Ltd. of Seattle, Wash. provides a system comprising modules for controlling the application of power to appliances connected thereto in accordance with control signals generated by a controller and communicated over 110 VAC power lines. Like the modules, the controller plugs into the power lines. Each module includes a switch for selecting one of a plurality of identifiers by which the module is addressed by the controller, thereby allowing a plurality of appliances in a household to be controlled individually by one controller. The X10 system also includes a wireless controller which communicates via RF with a unit which is plugged into the power lines. The system can also communicate with devices such as battery-powered passive infrared motion detectors and other security-related devices via radio frequency (RF) links. The X10 system also includes a computer interface allowing a personal computer (PC) to control and program the system.
Systems such as the aforementioned suffer from several limitations and drawbacks. For example, the degree of control is limited to simply turning appliances on and off. There is no capability of communicating information between the controller and the appliances or among the appliances. Moreover, the aforementioned system does not provide a method of adding components and modifying the system which is user-friendly and flexible while providing a high degree of security.